OnThu, 19 Mar 2015 09:30:56 -0700
<https://www.mail-archive.com/[email protected]&q=date:20150319>,
Richard Cochran wrote:
> Here is a random metric from the boards on my desk. The CPUs are the
> TI AM335x, but using the DP83640 PHY as the PTP Hardware Clock. The
> slave is directly connected to the master with 1 meter cable over a
> 100 Mbit link.
>
> Measuring the edges of a 1 kHz output at various Sync rates, and with
> a DelayReq rate of 1 Hz, I see the following differences.
>
> Rate Offset
> ----------------
> 2^0 +/- 75 ns
> 2^-3 +/- 25 ns
> 2^-4 +/- 20 ns
> 2^-5 +/- 20 ns
>
> As expected, increasing the DelayReq rate to 2^-5 makes no difference.
>
> So with this hardware, I have already reached the limit of
> synchronization performance. Increasing the Sync rate to 512 frames
> per second would not improve the picture.
>
> In contrast, using SyncE on the exact same hardware immediately yields
> an offset of +/- 1 nanosecond. (Actually, it probably is smaller, but
> I can't measure it with my lousy scope.)
Hi Richard,
Out of curiosity how do you use SyncE on this hardware ?
I can't see the DP83640 doing SyncE.
Xav
------------------------------------------------------------------------------
_______________________________________________
Linuxptp-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/linuxptp-users
